Study of a micro-structured PHE for the thermal management of a fuel cell

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.In the constantly growing market of fuel cells, the heat management of the system is a crucial area of research, since it affects the efficiency, operability and lifetime of the fuel cell. The CFD simulations performed for a plate heat exchanger (PHE) with flat plates clearly demonstrate temperature non-uniformity across the membrane of the unit cell. The CFD code was successfully validated with experimental data acquired from a setup that reproduces the geometry and simulates the thermal behaviour of a typical unit PEMFC. Additionally, the performance of a novel PHE, with micro-structured corrugations on its plates, was studied with the previously validated CFD code. The results clearly show that the proposed plate modifications can increase temperature uniformity across the membrane more than 20% compared to that of the flat plate

Co-current horizontal flow of a Newtonian and a non-Newtonian fluid in a microchannel

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.In this work, the flow of two immiscible liquids in a glass microchannel, I.D.= 580μm, was exper-imentally investigated. Various aqueous glycerol solutions containing xanthan gum were the non-Newtonian fluids, while kerosene was the Newtonian one. The flow rate of the non-Newtonian fluids varied from 50 to 200μL/min, while the kerosene flow rate was kept constant. The two fluids were put in contact at a T-junction. Visual observations were made using a high speed CCD camera and data were collected by processing the corresponding video images. The flow pattern was slug flow irrespective of the fluid that initially filled the microchannel. The experimental results revealed that the length of the kerosene slugs decreases by increasing either the aqueous phase flow rate or its viscosity. Furthermore the non-Newtonian fluid results in smaller and more frequent slugs than the corresponding Newtonian one. Thus by rendering a fluid non-Newtonian the interfacial area increases and consequently the mass transport performance is enhanced. This observation is expected to aid to the optimal design of two-phase microreactors. More work is certainly needed to investigate the effect of all the design parameters on the characteristics of this kind of flow in microchannels

Characterization of fluid flow in a microchannel with a flow disturbing step

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The flow around a flow-disturbing step in a rectangular microchannel is studied by measuring the wall shear rate along the channel, using the electrodiffusion technique and by determining the velocity field using the -PIV method. A parametric study based on the Design of Experiments (DOE) and the Response Surface Methodology (RSM) was then performed, and the effect of key design parameters on the flow characteristics was numerically investigated using CFD simulations. The computational results are in excellent agreement with the corresponding experimental ones. The CFD simulations cover both the laminar and the turbulent flow regime. It was revealed that in both flow regimes the step height has a major influence on the recirculation length. However, the Reynolds number (Re) value affects the recirculation length only in the laminar region, while the step length seems to have no significant effect compared to the Re and the step height. Finally, new correlations are proposed predicting the length of the bottom recirculation zone with reasonable accuracy and can be used as rough guidelines for the design of microdevices

iNCOVACC COVID-19 vaccine: A Twitter based Social Media Analysis Using Natural Language Processing, Sentiment Analysis, and Topic Modelling

Most, if not all, the vaccine candidates designed to counteract COVID-19 due to SARS-CoV-2 infection require parenteral administration. Mucosal immunity established by vaccination could significantly contribute to containing the SARS-CoV-2 pandemic, which is spread by infected respiratory secretions. The world has been impacted on many fronts by the COVID-19 pandemic since early 2020 and has yet to recover entirely from the impact of the crisis. In late 2022 and early 2023, China experienced a new surge of COVID-19 outbreaks, mainly in the country's northeastern region. With the threat of new variants like XBB 1.5 and BF.7, India might experience a similar COVID-19 surge as China and needs to be prepared to avoid destruction again. An intranasal vaccine can elicit multiple immunological responses, including IgG neutralization, mucosal IgA production, and T-cell responses. In order to prevent further infection and the spread of COVID-19, local immune responses in the nasal mucosa are required. iNCOVACC is a recombinant vaccine vectored by an adenovirus that contains a SARS-CoV-2 spike protein that has been pre-fusion stabilized. This vaccine candidate has shown promise in both early and late-stage clinical trials. iNCOVACC has been designed for intranasal administration via nasal drops. The nasal delivery system was created to reduce expenses for those living in poor and moderate-income countries. The newly introduced intranasal COVID vaccine will be beneficial in mass immunizing the public as it does not need any syringe and can be proven to be an effective method to boost immunity against the SARS-CoV-2 virus. This study uses natural language processing (NLP) techniques to analyze the Indian citizen's perceptions of the newly developed iNCOVACC vaccine in social media. For this study, we have used social media posts (tweets) as data. We have analyzed 125,300 tweets to study the general perception of Indian citizens regarding the iNCOVACC vaccine. Our results have indicated 43.19% of social media posts discussing the COVID-19 nasal vaccine in a neutral tone, nearly 34.29% of social media posts are positive, and 22.5% of social media posts discussions are negative. The general positive feeling that the iNCOVACC vaccine will work and the risks in the new vaccine are the two significant aspects Indian citizens voice out in social media posts about the iNCOVACC vaccine

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Experimental and Numerical Studies in Biomedical Engineering

The term ‘biomedical engineering’ refers to the application of the principles and problem-solving techniques of engineering to biology and medicine. Biomedical engineering is an interdisciplinary branch, as many of the problems health professionals are confronted with have traditionally been of interest to engineers because they involve processes that are fundamental to engineering practice. Biomedical engineers employ common engineering methods to comprehend, modify, or control biological systems, and to design and manufacture devices that can assist in the diagnosis and therapy of human diseases. This Special Issue of Fluids aims to be a forum for scientists and engineers from academia and industry to present and discuss recent developments in the field of biomedical engineering. It contains papers that tackle, both numerically (Computational Fluid Dynamics studies) and experimentally, biomedical engineering problems, with a diverse range of studies focusing on the fundamental understanding of fluid flows in biological systems, modelling studies on complex rheological phenomena and molecular dynamics, design and improvement of lab-on-a-chip devices, modelling of processes inside the human body as well as drug delivery applications. Contributions have focused on problems associated with subjects that include hemodynamical flows, arterial wall shear stress, targeted drug delivery, FSI/CFD and Multiphysics simulations, molecular dynamics modelling and physiology-based biokinetic models

An investigation of channel flow with a smooth air-water interface

Published online: 9 June 2015. This article belongs to a Topical Collection of articles entitled Extreme Flow Workshop 2014. Guest Editors: I. Marusic and B. J. McKeon.Experiments and numerical simulation are used to investigate fully developed laminar and turbulent channel flow with an air–water interface as the lower boundary condition. Laser Doppler velocimetry measurements of streamwise and wall-normal velocity components are made over a range of Reynolds number based upon channel height and bulk velocity from 1100 to 4300, which encompasses the laminar, transitional and low Reynolds numbers turbulent regimes. The results show that the airflow statistics near the stationary wall are not significantly altered by the air–water moving interface and reflect those found in channel flows. The mean statistics on the water interface side largely exhibit results similar to simulated Poiseuille–Couette flow (PCF) with a solid moving wall. For second-order statistics, however, the simulation and experimental results show some discrepancies near the moving water surface, suggesting that a full two-phase simulation is required. A momentum and energy transport tubes analysis is investigated for laminar and turbulent PCFs. This analysis builds upon the classical notion of a streamtube and indicates that part of the energy from the pressure gradient is transported towards the stationary wall and is dissipated as heat inside the energy tubes, while the remainder is transmitted to the moving wall. For the experiments, the airflow energy is transmitted towards the water to overcome the drag force and drive the water forward; therefore, the amount of energy transferred to the water is higher than the energy transferred to a solid moving wall.Reza Madad, John Elsnab, Cheng Chin, Joseph Klewicki, Ivan Marusi